A device for focusing an optical beam

Abstract

The focusing device comprises a housing and, within the housing, a scanning mechanism with two oscillating scanning mirrors arranged at the entrance of a focusing optics. One or two sources associated with the scanning mechanism generate secondary optical beams to assist focusing by means of a dynamic triangulation focusing system

Description

A DEVICE FOR FOCUSING AN OPTICAL BEAMDESCRIPTIONTECHNICAL FIELD

[0001] Th present invention relates to a device for focusing an optical beam, especially a laser beam. Embodiments disclosed herein relate in particular to a device for focusing a laser beam for surgical use, which can be associated with a viewing system. Although the embodiments disclosed herein are particularly related to surgical use, the innovations forming the subject of the present description may also find application in other fields, for example in combination with industrial lasers.BACKGROUND ART

[0002] The use of lasers in various surgical procedures has become a standard, particularly in otorhinolaryngology, in gynecology and other medical fields.

[0003] The main laser used in surgical applications is the CO2 laser, which emits at a wavelength in the far infrared band of 10,600 nm, since this wavelength is absorbed by all organic tissues (skin, muscles, mucous membranes, cartilage, fat, etc.).

[0004] The action of the CO2 laser beam is optimal when the beam is perfectly focused on the tissue to be treated. A focused laser beam has a very high power density, which makes it possible to sublimate the affected tissue. The surgeon can thus cut or ablate (remove layer by layer) the various tissues without creating thermal damage to the surrounding or underlying tissue.

[0005] In addition to directing the laser beam to the area to be treated, the operator must be able to focus it precisely on that surface. For this purpose, a focusing optics is associated with the laser source.

[0006] During the operation, the surgeon may change the viewing position and vary the distance of the surgical microscope in order to have optimal access to the operating area. Therefore, the focusing optics must have a variable focal length. Since the power laser beam entering the focusing optics has a small diameter, generally from 4 mm to 8 mm, in order to be focused at a distance of 200 mm to 600 mm and to obtain asufficiently small spot, i.e. having a sufficiently high power density and allowing very precise cutting, it is useful for the focusing optics also to function as a beam expander with an expansion ratio of, for example, 3.2x. In other words, the power laser beam enters the focusing optics with a diameter of about 6 mm and exits it with a diameter of 6x3.2=19 mm, and converges toward the focal point. At the focal distance set, for example 300 mm, it becomes a very small spot, in which the full power of the laser beam is concentrated.

[0007] The CO2 laser beam is invisible. In order to view the position where the power laser beam impinges on the tissue to be treated, a low-power aiming laser beam is used, having a wavelength in the visible range, generally red. The aiming beam is generated by an aiming source. The aiming beam is coaxial with the power laser beam and is focused by the focusing optics in the same manner as the power laser beam. The operator uses the aiming beam as a guide.

[0008] One of the major difficulties encountered during surgical operations with a laser micromanipulator is to focus the power laser beam perfectly on the surface of the tissue to be treated. Indeed, a power laser beam that is not perfectly focused is like a poorly sharpened scalpel. Moreover, when working with an unfocused beam there is a risk of causing thermal damage to the tissues surrounding and underlying the operating area.

[0009] Normally, the surgeon focuses the invisible power laser beam by focusing the aiming beam, which is visible. In other words, the surgeon acts on the focus adjustment system to minimize the diameter of the spot formed by the aiming beam impinging on the tissue.

[0010] However, a focus adjustment carried out in this manner may cause gross errors, since it is very difficult to determine the exact focusing of a visible laser beam by evaluating the diameter of the spot on the incident surface. Moreover, the focusing optics may have a considerable difference in depth of field between the power laser beam and the aiming beam, due to the different wavelengths of these beams. Consequently, although the aiming beam appears to be focused on the surface, the power laser beam could be out of focus.

[0011] Conversely, it would be desirable to be able to focus the power laser beam onthe surface of the tissue to be treated with a maximum error of +Z-2.5 mm. Within this limit, the cut is sharp and free of thermal effects. Beyond this limit, the cut made with the laser spot becomes inaccurate and ragged, with carbonization at the edges. Achieving focusing within these limits by relying solely on the spot of the aiming beam is extremely difficult, because the depth of field of the aiming beam is much greater than that of the power beam, and therefore the spot of the aiming beam impinging on the surface appears well focused even when the distance of the incident surface varies by + / -6 mm. Consequently, the surgeon is often forced to perform test shots and to assess the correct focusing by evaluating the size of the power laser spot.

[0012] An aid to focusing is achieved with so-called triangulation systems, which exploit a typical feature of focusing lenses or optics. By making two aiming beams, misaligned in relation to each other and parallel to the optical axis, enter the focusing optics, the corresponding two beams exiting the focusing optics generate, on the incident surface, two distinct spots which will collimate into a single spot only when the incident surface is at the exact focal distance from the focusing optics. With this system, before operating the surgeon can check the exact focusing by activating the two aiming beams and performing the focusing operation.

[0013] These focusing systems are not widely used because they have many drawbacks. In particular, the two aiming beams must enter the focusing optics perfectly parallel to the optical axis of the optics. This condition requires stable and precise machining operations and systems for adjusting the direction of the two aiming beams, since a slight misalignment between the aiming beams would prevent the two spots from coinciding on the focal plane.

[0014] Moreover, some types of focusing optics are not perfectly achromatic, that is, they have small differences in the position of the focal planes at the two wavelengths of the aiming beams and of the power optical beam to be focused. In other cases, the laser source connected to the focusing optics could generate a power laser beam that is not perfectly collimated. These conditions mean that, even if the two aiming beams entering the focusing optics are perfectly aligned, the focal plane in which they collimate is not necessarily exactly coincident with the focal plane of the power laser beam.

[0015] The object of the present invention is to solve or to alleviate the problems of the prior art focusing devices. In particular, embodiments disclosed herein aim at allowing focusing with high precision without the need for precision mechanical workmanship, which is costly and difficult to achieve.SUMMARY

[0016] In summary, embodiments disclosed herein relate to a focusing device comprising a focusing optics combined with a scanning mechanism and an optical assembly for generating secondary beams, for performing focusing by means of dynamic triangulation, in which the high precision required by static triangulation - achievable only through demanding mechanical machining operations - is replaced with equally high precision achievable electronically by acting on the scanning mirrors of the scanning mechanism associated with the focusing optics.

[0017] In embodiments of the invention, a device is provided for focusing an optical beam, particularly a laser beam, which comprises a housing with an entrance opening for the optical beam to be focused and an exit opening for the optical beam to be focused. A focusing optics having an optical axis, and a scanning mechanism for the optical beam to be focused, arranged between the entrance opening and the focusing optics, are provided in the housing. The scanning mechanism comprises a first scanning mirror along an optical path between the entrance opening and the focusing optics, and a second scanning mirror along the optical path between the entrance opening and the first scanning mirror. The second scanning mirror is positioned so as to reflect the optical beam to be focused, which enters the housing through the entrance opening, toward the first scanning mirror. The first scanning mirror is controlled by an actuator that controls a scanning movement of the first scanning mirror around a first scanning axis. The second scanning mirror is controlled by an actuator that controls a scanning movement of the second scanning mirror around a second scanning axis that is not parallel to the first scanning axis. An optical assembly generates two secondary beams for assisting focusing. The optical assembly for generating secondary beams is configured to emit a first secondary optical beam and a second secondary optical beam, both at a visible wavelength and mutually misaligned.

[0018] The scanning mechanism, the focusing optics, and the optical assembly forgenerating secondary beams are configured to selectively take a first operating condition, a second operating condition, and a third operating condition.

[0019] In the first operating condition, the optical beam to be focused impinges on the second scanning mirror and is directed by the scanning mechanism within an acceptance angle of the focusing optics. In the second operating condition, the first secondary optical beam and the optical beam to be focused do not pass through the focusing optics; and the second secondary optical beam impinges on the second scanning mirror and is directed by the scanning mechanism within the acceptance angle of the focusing lens, in a direction parallel to, but spaced from, the optical axis of the focusing optics. In the third operating condition, the second secondary optical beam and the optical beam to be focused do not pass through the focusing optics; and the first secondary optical beam impinges on the second scanning mirror and is directed by the scanning mechanism within the acceptance angle of the focusing lens, in a direction parallel to, and spaced from, the optical axis of the focusing optics.

[0020] According to embodiments disclosed herein, during a focusing phase, the scanning mechanism, the focusing optics, and the optical assembly for generating secondary beams are controlled so as to switch from the second operating condition to the third operating condition and vice versa at a speed higher than the persistence time - on the retina of the eye of an observer viewing a target surface on which the optical beam is to be focused - of an image of a spot of the first secondary optical beam and of the second secondary optical beam on the target surface.

[0021] The condition in which a given beam (for example the beam to be focused, or the first or the second secondary optical beam) does not pass through the focusing optics may be achieved in various ways. According to some embodiments, this condition may be achieved by switching off the source that generates the optical beam. According to other embodiments, the condition in which the beam does not pass through the focusing optics is achieved by intercepting the respective beam along its propagation path. In yet further embodiments, the condition in which the beam does not pass through the focusing optics is achieved by directing the beam so that it cannot propagate through the focusing optics, as it is directed outside the acceptance angle of the focusing optics. The three modes may be combined with one another.

[0022] The focusing optics may comprise a fixed focusing lens and a movable optical element. The movable optical element may comprise an element having optical power in transmission, namely a lens.

[0023] In some embodiments, the movable optical element comprises - or consists of - a concave mirror. In some embodiments, the concave mirror is provided with a translatory focusing movement along a focusing axis, and with a scanning movement around a neutral position. In this case, the concave mirror comprises an optical axis parallel to the axis of the fixed focusing lens when the concave mirror is in the neutral position. In other embodiments, the concave mirror is provided with a translatory focusing movement along a focusing axis, but without a scanning movement. In this case, the concave mirror is coaxial with the fixed focusing lens.

[0024] In summary, by exploiting the precision and speed characteristics of a scanning mechanism, i.e. of a scanner, a new focusing aid system has been provided, that is capable of generating, at the output of the scanning mechanism, and thus at the input of the focusing optics, two secondary optical beams, specifically two secondary laser beams, perfectly parallel to the optical axis of the focusing optics and mutually offset, which replicate exactly what occurs in a static triangulation focusing system of the prior art, as described above, but with the feature that the device is much easier to manufacture, and does not require complex mechanical machining or alignments.

[0025] A significant improvement of the dynamic triangulation focusing achieved by exploiting the scanning mechanism at the input of the focusing optics is that the adjustment of the direction of the secondary optical beams is electronic, and can be easily and extremely precisely adapted to various operating conditions. The stability and precision required for exact triangulation focusing are ensured by the stability and precision of the scanning mechanism, which are features intrinsic to the scanning mechanism.

[0026] Moreover, by exploiting the high speed and precision of the scanning mechanism, it is possible to generate, on the focal plane, not merely two simple points or spots that collimate only on the focal plane, but rather two more complex and more easily visible patterns, for example two lines, or two figures defined by closed lines, for example two circumferences, two triangles, or other closed figures. These figurescollimate, that is, are superimposed on each other, only on the focal plane. In some embodiments, it is possible to generate two figures defined by two closed lines of equal shape but different size, typically two circumferences of different radii, for example. In this case, focusing is achieved when the two circumferences appearing on the plane of incidence of the aiming beams are concentric with each other. This greatly assists the operator in finding the exact focal point with extremely high precision, which is difficult to achieve with other systems.

[0027] As with the adjustment of the direction of the two secondary optical beams, the shape, orientation and dimensions of the patters that collimate only on the focal plane are also generated electronically, and therefore can be easily adjusted and modified.BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The invention shall be better understood by following the description and the accompanying drawings, which show non-limiting examples of embodiment of the invention. More particularly, in the drawings:Fig. 1 is an external side view of a device for focusing and directing an optical beam in an embodiment;Fig. 2 is a view according to II-II in Fig. 1;Fig. 3 is a view according to III-III of Fig. 2;Fig. 4 shows a cross-section according to IV-IV of Fig. 3;Fig. 5 is an axonometric view of the device of Figs. 1 to 4;Fig. 6 is a sectional axonometric view of the device of Figs. 1 to 5;Fig. 7 shows a section according to VII- VII of Fig. 3;Fig. 8 is an axonometric view of the support and the mechanism for directing the concave mirror;Fig. 9 is an exploded view of the support and the direction mechanism shown in Fig. 8;Fig. 10 a schematic representation of the optical paths of the main optical beam in the device of Figs. 1 through 9;Fig. 11 is an enlargement of a portion of Fig. 10;Fig. 12 is a schematic representation of the optical paths of the auxiliary optical beams;Fig. 13 shows an enlargement of a portion of Fig. 12;Fig. 14 a schematic side view of a further embodiment of the focusing system in a first operating condition;Fig. 15 is a view according to XV-XV of Fig. 14;Fig. 16 is an axonometric view of the device of Figs. 14 and 15;Figs. 17, 18 and 19 show views analogous to those of Figs. 14, 15 and 16 in a second operating condition;Figs. 20, 21 and 22 show views analogous to those of Figs. 14, 15 and 16 in a third operating condition; andFig. 23 is a view analogous to that of Fig. 15 in a further embodiment.DETAILED DESCRIPTION

[0029] The following description refers to a device for focusing and directing an optical beam, particularly a laser beam, in the context of a laser surgery lens. However, it should be understood that the components described below for focusing and directing the beam could be advantageously used also in other contexts, whenever it is necessary to focus and to direct an optical beam, especially a laser beam. Therefore, some of the elements described below may be omitted or replaced by others, depending on the use of the device. For example, the scanning mechanism, which imparts a fast scanning movement to the beam entering the lens, could be omitted.

[0030] With initial reference to Figs. 1 through 6, the focusing and directing device 1, here below also referred to briefly as "device", comprises a housing 3, in which most of the optical components of the device 1 are housed.

[0031] The housing 3 comprises an entrance opening 4 and an exit opening 5. The entrance opening 4 can be configured to be coupled to one end of an articulated arm forming a light guide for a laser beam, or generically an optical beam, coming from a source, for example a CO2 laser, not shown. In the following description, reference will be made specifically to a laser source and a laser beam, but innovative features of the device disclosed herein can in some cases also be used in combination with optical beam sources of other kinds.

[0032] As it will be detailed below, in the housing 3 the following are in particular housed: a fast scanning mechanism, to impart a fast scanning movement around twoaxes to an incoming laser beam; a focusing lens; a first flat reflecting surface and a concave mirror for focusing and directing, i.e. slow scanning, the beam. In some embodiments described herein, the slow scanning, that is, the direction movement, is according to two axes of rotation, preferably orthogonal to each other.

[0033] Furthermore, electronic components and actuators are housed in the housing 3, that impart the scanning, focusing and directing movements of the laser beam, and that will be described in more detail below.

[0034] A semi-transparent flat surface is arranged in front of the exit opening 5, the surface consisting, in the specific example, of a semi-transparent flat mirror 9 inclined relative to an axis of propagation of the laser beam exiting from the housing 3 through the exit opening 5. The semi-transparent flat mirror 9 is connected to the housing or casing 3 by means of a support bracket 7, for example, and is arranged outside the housing 3. A microscope, a surgical stereo microscope, a colposcope, a surgical 3D exoscope, a video camera, or any other viewing or image acquisition system can be arranged in front of the semi-transparent flat mirror 9. The viewing system is schematically indicated with the reference number 11. Al l indicates the optical axis of the viewing system 11.

[0035] The semi-transparent flat mirror 9 allows to direct the laser beam, coming from the device 1, through the exit opening 5, toward an operating area, also referred to hereafter as “target area”. The viewing system 11 (and thus the operator), through the semi-transparent mirror 9, can observe the surgical area impinged by the laser beam, for example, a laser beam from a CO2 laser, to perform cutting, ablation, or other operations on a patient's tissues. In addition to the main laser beam, coming for example from a CO2 laser, secondary or auxiliary beams, generated by sources contained in the housing 3 and described below, can be conveyed toward the operating area to facilitate aiming and / or focusing, the beams having a frequency in the visible band.

[0036] The components described below are arranged inside the housing 3, following the optical path from the entrance opening 4 to the exit opening 5.

[0037] A scanning mechanism 13 is provided directly in front of the entrance opening 4, the mechanism comprising one or more mirrors driven with a fastoscillatory motion by suitable galvanometers, or other suitable actuators. In the present description, the term "fast" means a movement that is substantially faster than that with which the optical beam is moved along the axes Ax, Ay defined below.

[0038] In the illustrated embodiment, the scanning mechanism comprises two scanning mirrors, typically two flat mirrors, with two respective actuators, each of which makes the respective mirror oscillate fast around a respective axis of oscillation. The two axes of oscillation are non-parallel to each other and preferably directed at 90° relative to each other. However, it is also possible to provide a scanning mechanism with a single scanning mirror having a fast scanning movement around two orthogonal or otherwise mutually inclined axes.

[0039] Specifically, in the illustrated embodiment, the scanning mechanism 13 comprises a first scanning mirror 15 controlled by a first actuator 17, such as a galvanometer, so as to oscillate around a fast scanning axis 15A (see Fig. 4). The scanning mechanism also comprises a second scanning mirror 19 controlled by a second actuator 21, such as a galvanometer, so as to oscillate around a second fast scanning axis 19 A. The two axes 15 A, 19A are not parallel to each other. In the illustrated embodiment, the two axes 15 A, 19A are skewed and oriented at 90° relative to each other.

[0040] The optical path of a laser beam entering through the entrance opening 4 firstly encounters the scanning mirror 19 and then the scanning mirror 15. Thus, the terms "first" and "second" do not refer to the sequence along the optical path, and are merely conventional.

[0041] A focusing optics is arranged inside housing 3, in front of the scanning mechanism 13, and more precisely in front of the first scanning mirror 15. In some embodiments, the focusing optics consists of a variable-focal-length expander lens. In embodiments described herein, the focusing optics comprises a focusing lens 23, whose optical axis is indicated with the reference A23. The focusing lens 23 is stationary relative to the housing 3. The focusing lens 23 comprises one or more converging lenses to converge a collimated laser beam coming through the entrance opening 4 from an external laser source, not shown.

[0042] In some embodiments, the focusing lens 23 is based on the use of a specialtype of converging lens called "hybrid lens", used to focus laser beams with significantly different wavelengths, such as the primary CO2 beam with a wavelength of 10.6 micrometers, and a secondary red aiming beam with a wavelength of 0.635 micrometers. By focusing two laser beams with such different focal lengths by means of a "hybrid" lens, it is possible to substantially reduce the chromatic aberration that occurs with the use of a conventional lens and that causes the red aiming beam to be focused on a plane of focus far away from the plane of focus of the main laser beam. The "hybrid" lens solves this problem through a diffractive pattern provided on one of the entrance and exit surfaces. This pattern is transparent to the beam generated by the CO2 laser, and is instead seen by the red beam as a corrective lens that shifts the plane of focus, making it coincide with the plane of focus of the main beam generated by the CO2 laser.

[0043] A flat reflecting surface, which consists, in this embodiment, of a flat mirror 25, is provided in front of the focusing lens 23, on the exit side, opposite the entrance side where the scanning mechanism 13 is arranged. The flat mirror 25 is inclined at an angle a equal to 45° relative to the optical axis A23 of the focusing lens 23.

[0044] The flat mirror 25 has a central hole 26, shown particularly in the axonometric section of Fig. 6. The hole 26 is advantageously placed at such a distance from the focusing lens 23 that the focus of the focusing lens 23 is within the hole 26. In this way, the entire energy of the laser beam focused by the focusing lens 23 passes through the flat mirror 25 using a hole 26 of very small diameter, minimizing the loss of reflecting surface of the flat mirror 25.

[0045] Continuing along the optical path within the device 1, a concave mirror 27 is provided in front of the flat mirror 25; the concave mirror constitutes a movable optical element of the focusing optics that therefore consists of (in this embodiment) the fixed focusing lens 23 and the concave mirror 27. As it will be better explained below, the concave mirror 27 has a translatory focusing movement along a focusing axis, parallel to the optical axis A23, which constitutes the optical axis of the focusing optics. Furthermore, in this embodiment, the concave mirror 27 has a rotary movement around two rotary axes orthogonal to each other and orthogonal to the optical axis A23. The axes of rotation of the concave mirror 27 are indicated with Ax and Ay in Fig. 6. In practice, the concave mirror 27 has a rest position, where its optical axis coincides withthe optical axis 23 A of the focusing lens and is therefore parallel to the focusing axis Az.

[0046] By means of an oscillation mechanism, described below, the concave mirror 27 can perform a scanning movement, that is, it can oscillate by a limited angle, for example + / - 4°, around the rest position, so that its optical axis moves within a scanning cone having a vertex angle of 8°. The scanning cone is indicated with CS in Fig. 8. It should be understood that the value of the oscillation angle is merely indicative and illustrative, and should not be interpreted as limiting.

[0047] In the illustrated embodiment, the concave mirror 27 is mounted on a support 29 provided with a movement according to the arrow f29, parallel to the focusing axis Az, and thus to the optical axis A23 of the focusing lens 23. The support 29 can be mounted in a cylinder 31, housed in the housing 3 and movable within the housing along the direction f29. The movement of the movable cylinder 31, and thus of the support 29, can be controlled by means of an external ring 33, connected to the movable cylinder 31 via a screw coupling 34. The movement of the ring 33 can be controlled manually.

[0048] Alternatively, or in combination, the movement of the ring 33 can be controlled by an actuator, for example an electric motor 37, through a reduction gear unit 39 contained in the housing 3. In some embodiments, a release mechanism may be provided to control the rotation of the ring 33 alternately by hand or by means of the electric motor 37 and the associated reduction gear 39. The release mechanism is indicated with the reference number 41 and comprises, for example, a lever that allows two gear wheels of the reduction gear 39, normally meshing with each other, to be moved away from each other so as to release the electric motor 37 from the ring 33.

[0049] The concave mirror 27 is constrained to the support 29 so as to oscillate around the axes Ax, Ay that are orthogonal to each other and orthogonal to the axis A23. Moreover, a direction mechanism 43 is mounted on the support 29 to direct the concave mirror 27 by making it oscillate around the axes Ax, Ay. Figs. 8 and 9 show a further embodiment of these components.

[0050] In this embodiment, the direction mechanism 43 comprises a first actuating member adapted to rotate or to oscillate the concave mirror 27 around the first axis Axof rotation, and a second actuating member adapted to rotate or to oscillate the concave mirror 27 around the second axis Ay of rotation. In the illustrated embodiment, each actuating member comprises a pair of electromagnetic actuators, described below.

[0051] The direction mechanism 43 also comprises an elastic system 47, connecting the concave mirror 27 to the support 29 and defining a minimum elastic energy position, where the optical axis of the concave mirror 27 is parallel to the focusing axis Az and coincides with the optical axis A23 of the focusing lens 23. The elastic system 47 is configured to generate elastic forces that counteract the rotation of the concave mirror 27 around the first rotation axis Ax and around the second rotation axis Ay.

[0052] The position where the optical axis of the concave mirror 27 is parallel to (or coincident with) the focusing axis Az is a "neutral" position of the concave mirror 27.

[0053] For example, the concave mirror 27 may be integral with an oscillating equipment 49, connected to the support 29 through the elastic system 47. The oscillating equipment 49 oscillates according to the double arrows fx, fy around the axes Ax and Ay and can translate, integrally with the support 29, in the focusing direction f29, parallel to the focusing axis Az.

[0054] In some embodiments, the first actuating member comprises a first pair of electromagnets 51. Each electromagnet 51 comprises an electromagnetic coil 51.1 and a movable magnetic armature 51.2, coaxial with, and internal to, the electromagnetic coil 51.1. The electromagnetic coils 51.1 of the first pair of electromagnets 51 are arranged with their axes parallel to the focusing axis Az and on a plane containing the focusing axis Az and the second rotation axis Ay. The electromagnetic coils 51.1 of the first pair of electromagnets 51 are electrically connected in series so as to generate, when current flows through them, a torque adapted to rotate the oscillating equipment 49, and the concave mirror 27 mounted on it, around the first axis of rotation Ax.

[0055] Similarly, the second actuating member comprises a second pair of electromagnets 53. Each electromagnet 53 comprises an electromagnetic coil 53.1 and a movable magnetic armature 53.2, coaxial with, and internal to, the electromagnetic coil 53.1. The electromagnetic coils 53.1 of the second pair of electromagnets 53 are arranged with their axes parallel to the focusing axis Az and on a plane containing the focusing axis Az and the second rotation axis Ax. The electromagnetic coils 53.1 ofthe second pair of electromagnets 53 are electrically connected in series so as to generate, when current flows through them, a torque adapted to rotate the oscillating equipment 49, and the concave mirror 27 mounted on it, around the second axis of rotation Ay.

[0056] In some embodiments, the elastic system comprises a double leaf spring 61, comprising: a first pair of arms 61.1, aligned with each other and attached, at their distal ends, to the oscillating equipment 49, and a second pair of arms 61.2, aligned with each other, generally orthogonal to the first pair of oscillating arms 61.1 and attached, at their distal ends, to the support 29. The arms extend from a central core centered with respect to the concave mirror 27 and the support 29.

[0057] The operation of the focusing and directing device 1 described above is explained below with reference also to Figs. 10 and 11, which show the optical path of the laser beam.

[0058] A collimated laser beam coming from a source, not shown, enters the device (arrow F, Figs. 4, 10, 11) through the entrance opening 4 and is reflected by the second scanning mirror 19 and the first scanning mirror 15. The first scanning mirror directs the laser beam toward the focusing lens 23, which focuses the beam inside the hole 26 of the flat mirror 25. The focused beam exits the hole 26, and thus the surface of the flat mirror 25, to propagate toward the concave mirror 27, on which the laser beam arrives partially expanded as it diverges downstream of the focus of the focusing lens 23.

[0059] The concave mirror 27 reflects the laser beam and focuses it in a focus at an appropriate focal distance, which is a function, for example, of the type of application of the device 1. The focus of the concave mirror 27 is outside the device 1. The optical path of the converging laser beam F2 reflected by the concave mirror 27 propagates from the concave mirror 27 toward the flat mirror 25, which reflects the converging laser beam toward the exit opening 5 (beam F2 in Fig. 4, 10, 11). The semi-transparent mirror 9, provided in front of the exit opening 5, reflects the converging laser beam (arrow F3, Figs. 1, 10, 11) toward the working zone or target area AT (Figs. 10, 11), for example an operating area, where there is the focus F27 of the concave mirror 27.

[0060] To focus the laser beam coming from the device 1 onto the area of interest,the ring 33 is operated manually, or through the motor 37. In the second case, the motor 37 can be interfaced with a programmable control unit, which can be connected to a human-machine interface (HMI), such as a touch pad, through which an operator can control the focusing movement.

[0061] In order to scan the area (target area AT, Fig. 10) on which the laser beam focused by the concave mirror 27 impinges, it is possible to impart a scanning movement to the concave mirror 27, consisting of rotary movements, i.e. oscillatory movements, around the axes Ax, Ay by means of the actuators of the direction mechanism shown in Figs. 8 and 9. Fig. 8 shows the scanning cone with a 8° aperture, which can be easily achieved by means of oscillatory movements of the concave mirror 27 around the axes Ax, Ay.

[0062] The oscillatory movements of the laser beam, i.e. the movement of slow scanning around the axes Ax, Ay, can be imparted by means of a human-machine interface, for example the same one by which the focusing movements are imparted through translation of the support 29 and the concave mirror 27 along the focusing axis Az, i.e. parallel to the optical axis A23 of the focusing lens 23.

[0063] In practice, the device 1 allows to perform all the movements necessary for focusing the laser beam onto the target area (e.g. the operating area) and the movements of the laser spot on the target area by means of combined movements along the rotary axes Ax, Ay and along the translatory focusing axis Az of the concave mirror 27 alone.

[0064] The operator can observe the operating area, or generally the target area, to which the laser beam, reflected by the semi-transparent flat mirror 9, is directed, by standing behind the mirror with respect to the propagation path of the laser beam F3. In practice, the operator can observe the treated area through a microscope arranged in 11 (Fig. 1) or, for example, on a monitor where an image is shown, taken by a video camera arranged in 11.

[0065] In contrast to the conventional devices, the semi-transparent mirror 9 is fixed relative to the casing or housing 3 where the other optical components of the device are arranged. Therefore, the directions, relative to the semi-transparent flat mirror 9, of the reflected laser beam F3 and of the beams coming from the operating area ortarget area, remain unchanged.

[0066] The need for a joystick or other member for moving the semi-transparent flat mirror 9 is eliminated, resulting in space-saving advantages. Also, there is no need to place bulky actuators outside the housing 3, in the area surrounding the semitransparent flat mirror 9. This is particularly advantageous because the area surrounding the mirror is used by the medical staff to access the operating area. Thus, the absence of actuators in the area surrounding the semi-transparent flat mirror 9 makes it easier to perform surgery (when the device 1 is for surgical use) or any other interventions to be performed with the device 1.

[0067] When the laser beam shall be moved with a fast scanning movement, the scanning mirrors 15, 19 can be placed in fast oscillation around the respective fast scanning axes 15 A, 19 A. In general, the fast scanning movements of the two scanning mirrors 15, 19 around the two fast scanning axes 15 A, 19A are coordinated with each other, so that the spot of the laser beam moves over the target area following a preset pattern.

[0068] The fast scanning movement is normally used, for example, to perform tissue ablation by combining the fast scanning movement, imparted to the scanning mirrors 15, 19, and the slow scanning movement around the axes Ax, Ay, imparted to the concave mirror 27.

[0069] Various above-described features of the focusing and directing device 1 allow to obtain significant advantages compared to the prior art devices.

[0070] With reference to the directing system (or slow scanning around the axes Ax, Ay) of the laser beam, the following is observed. The absence of friction, hysteresis phenomena, mechanical clearance and wear of the elastic suspension, achieved through the elastic system 47 and the electromagnetic actuators 51, 53 described above, allows smooth and precise movement of the concave mirror 27, with the possibility of aiming the spot, generated by the laser beam deflected by the concave mirror 27, onto the focal plane with micrometric resolution.

[0071] The deviation of the optical axis of the concave mirror 27 is proportional to the coil currents in the actuators 51, 53. In principle, this can allow the actuators 51,53 to be driven in an open loop.

[0072] However, in order to eliminate the effect of cross-talk phenomena between the arms of the elastic suspension formed by the double leaf spring 61, as well as the effect of the predominance of the moment of inertia of the oscillating equipment 49 over the resisting elastic moments, and thus in order to make the movement of the concave mirror 27 faster and more precise, it may be advantageous to provide closed- loop control of the position of the optical axis of the concave mirror 27 by means of a biaxial position sensor. The electronic board of a biaxial optical sensor usable for this purpose is indicated with the reference number 71. In advantageous embodiments, the absolute angular position of the optical axis of the concave mirror 27 can be detected by means of an amplified biaxial optical sensor equipped with an AGC (Automatic Gain Control) device for the suppression of thermal and ageing drift. The outputs of the amplified position sensor (PosX and PosY) vary proportionally to the inclination of the projection of the axis of the concave mirror 27 in the planes Ax- Az and Ay-Az, respectively.

[0073] Moreover, the orientation of the outgoing laser beam, obtained by the rotary movement of the concave mirror 27 around the axes Ax and Ay, makes it possible to obtain multiple advantages over traditional systems, which are based on directing the laser beam by moving the external semi-transparent mirror 9 around two mutually orthogonal axes of rotation. In particular, the overall dimensions of the device are reduced, especially in the area of the semi-transparent mirror 9, thus making the operating area more easily accessible. Indeed, the actuators that control the slow scanning of the laser beam along the axes Ax, Ay are located inside the housing 3 and not around the semi-transparent mirror 9.

[0074] Since the semi-transparent mirror 9 remains in a fixed position, the optical effects on the image acquired through the semi-transparent mirror 9, due to variations in the angle of incidence of the illumination cone of the microscope on the semitransparent mirror, are eliminated or reduced.

[0075] The arrangement of the scanning mechanism 13 inside the housing 1, instead of outside the entrance opening 4 as provided in the prior art devices, on the one hand allows to reduce the overall dimensions and the weight of the device 1, and, on theother hand, ensures a perfect alignment of the optical components of the system, that, once mounted inside the housing 3, maintain their mutual position and do not have to be realigned after assembly and disassembly operations. Moreover, compared with configurations where the scanning mechanism 13 is placed outside the housing 3, the illustrated embodiment allows to reduce the number of mirrors, or reflecting surfaces, along the optical path. In fact, the laser beam reflected by the scanning mirrors 19 and 15 is directly directed onto the focusing lens 23, without the need for further reflections and direction changes.

[0076] The integration of the fast scanning mirrors 15, 19 within the housing 3 makes it possible easily to provide a focusing aid system, which will be described below with particular reference to Figs. 7, 12 and 13.

[0077] It will be clearly apparent, from the description below, that the focusing aid system of the invention can also be used with a different focusing optics than the one described above. For example, in some embodiments the focusing optics may have a lens instead of a concave mirror. Also, in other embodiments, the concave mirror, if any, is not provided with the oscillatory movement around the axes X, Y. This oscillatory movement, in fact, has no relevance to the focusing-aid system described below. The aid system can work in exactly the same way as illustrated hereinafter, irrespective of the specific configuration of the focusing optics.

[0078] In the embodiment shown in Figs. 1 through 13, the focusing-aid system comprises a first auxiliary optical source 81 and a second auxiliary optical source 83, for example a laser source, typically a micro-laser. The two auxiliary optical sources 81, 83 - hereinafter also briefly referred to simply as "optical sources" - are housed inside the housing 3. Hereinafter, the optical sources 81 and 83 will be briefly referred to as micro-lasers. The two optical sources 81 and 83 form, in this example, an optical assembly for generating secondary beams, configured to emit a first secondary optical beam and a second secondary optical beam, both at a visible wavelength and mutually offset.

[0079] The two micro-lasers are fixed in the housing 3 behind the focusing lens 23 and outside the path of the main laser beam entering the focusing lens 23 through the entrance opening 4 by reflection on the scanning mirrors 19 and 15.

[0080] The two micro-lasers 81, 83 generate two secondary optical beams, in particular two secondary laser beams FS1, FS2 having a wavelength in the visible range. Thetwo secondary laser beams FS1, FS2 impinge on the surface of the scanning mirror 19. The points of incidence of the two secondary laser beams FS1, FS2 are offset in relation to the center of the scanning mirror 19, for example by about 3 mm on the right-hand and left-hand side, respectively, relative to the center of the mirror. As shown in the figures (see especially Figs. 7 and 13) the two micro-lasers 81, 83 are configured and directed in such a way that the two secondary laser beams FS1 and FS2 converge toward a point that is on the side of the second mirror 19 opposite to the micro-lasers 81, 83.

[0081] The micro-lasers 81, 83, the focusing lens 23 and the scanning mirrors 19, 15 are arranged in such a way that, under the normal conditions of use of the device 1, the secondary laser beams FS1, FS2 are reflected by the scanning mirror 19 outside the acceptance angle of the focusing lens 23 and are not visible outside the device, i.e. they are not projected onto the target area AT.

[0082] By clockwise rotating the scanning mirror 19 by a predetermined angle, for example about 7.5°, the secondary laser beam FS1 generated by the micro-laser 81 is reflected exactly in the direction of the optical axis A23 of the focusing lens 23, but spaced from this axis, for example about 3 mm on the left-hand side. When the scanning mirror 19 is in this position, both the main laser beam from the external source (beam F) and the secondary laser beam FS2 generated by the micro-laser 83 are reflected outside the acceptance angle of the focusing lens 23, are not visible outside, and therefore do not reach the target area AT.

[0083] Conversely, by counterclockwise rotating the scanning mirror 19 by, for example, an angle of about 7.5°, the secondary laser beam FS2 generated by the microlaser 83 is reflected exactly in the same direction of the optical axis A23 of the focusing lens 23, but spaced from this axis, for example about 3 mm on the right-hand side. When the scanning mirror 19 is in this position, both the main laser beam (F), coming from the external source, and the secondary laser beam FS1, generated by the microlaser 81, are reflected outside the acceptance angle of the focusing lens 23, and are not visible outside, and therefore do not reach the target area AT.

[0084] By quickly alternating the position of the scanning mirror 19 from 7.5° in the clockwise direction to 7.5° in the counterclockwise direction, secondary laser beams FS1, FS2 are obtained at the input of the focusing lens 23, which are parallel to the optical axis 23 of the focusing lens, but spaced symmetrically with respect to the optical axis A23 by about 6 mm. The movement of the scanning mirror 19 in the clockwise and counterclockwise directions, in order to selectively project either of the secondary beams FS1, FS2 within the acceptance angle of the focusing lens 23, is sufficiently fast to allow simultaneous viewing of the two spots formed on the target area AT by the two secondary laser beams FS1, FS2 thanks to the persistence of the image on the retina of the eye.

[0085] With the system described above, use id made of the characteristic of the focusing lens 23 of causing the spots, generated by the two secondary laser beams FS1, FS2 entering parallel to the optical axis A23 of the focusing lens 23, to coincide only on the focal plane of the device 1. Outside this plane, the two spots are spaced apart from each other.

[0086] By suitably modulating the actuators 17, 21 of the fast scanning mechanism 13, it is possible to generate two lines or any other patterns that coincide only on the focal plane of the optics comprising the focusing lens 23 and the concave mirror 27. In practice, it thus becomes easy and simple to position the concave mirror 27 (the only focusing element movable along the optical path of the laser beam) in such a way that the focus lies on the target area AT.

[0087] The focusing operation consists in moving the concave mirror 27 along the focusing axis Az by means of the ring 33, while the scanning mechanism 13 alternately projects the beam FS1 and the beam FS2 along the path parallel to the focusing axis A23, until the two patterns generated by the two spots as a result of the fast scanning movement of the scanning mirrors 15, 17 are superimposed on each other. When this occurs, the focus of the optical system 23, 27 lies on the target area AT.

[0088] Any small misalignments due to manufacturing and assembly tolerances of the two micro-lasers 81, 83 can be easily corrected by acting on the values of the signals sent to the control of the scanning mechanism 13, that is, on the positions of scanning mirrors 15 and 19.

[0089] This focusing aid system makes it possible to obtain significant advantages. Indeed, normally the operator attempts to focus the main laser beam (F at the input, F3 at the output of the device 1), which comes from the main laser source, for example a CO2 laser (which is invisible), by focusing onto the surface of the operating area, or target area AT, an aiming laser beam having a visible wavelength. This operation is not easy, both because the aiming laser beam is very small and has a large depth of field, and because there may be differences in focal distance between the aiming laser beam and the laser beam of the main source, which focal distance is due to the different wavelength of the two beams.

[0090] With the system described above, which uses the two micro-lasers 81, 83, two luminous patterns appear on the surface impinged by the laser beam exiting the device 1, for example two lines, two circles, two triangles or the like. By actuating the ring 33 manually or electrically from a remote location, the two patterns move apart from, or approach each other as the focal distance varies, and they are perfectly aligned only when the focal plane of the device 1 coincides with the surface of incidence, i.e. the target surface AT on which impinge the laser beams exiting the device.

[0091] In some embodiments, the two patterns are constituted, for example, by two closed lines, such as, by way of example, two circumferences or two ellipses. If the two closed lines are identical (in the case of circumferences, if they have the same diameter), they are perfectly superimposed when the focus of the focusing optics falls on the surface of incidence of the laser beam. In other embodiments, the two patters generated in rapid sequence by the two micro-lasers have, for example, the same shape but different dimensions; for instance, they may be circumferences of different diameters, or ellipses with major and minor axes differing from each other. The focus will lie on the surface of incidence of the laser beams when the two patterns are concentric to each other.

[0092] Circular, elliptical or other patterns made up of closed lines can easily be obtained by means of a coordinated movement of the two scanning mirrors.

[0093] This way of operating makes focusing of the main laser beam onto the operating surface simple, precise and intuitive, the main laser beam coming, for example, from a CO2 source, which is invisible to the human eye.

[0094] The device described above have multiple applications, among which those in the surgical field are particularly significant, as the described configuration of the device for focusing and directing the laser beam can easily be dimensioned in such a way as to direct and to guide the laser beam in a very narrow and long volume, such as is typically required in many surgical applications, for example, in the otolaryngology field.

[0095] Below, some parameters of the device are indicated, and the ranges these parameters may have especially in the case of applications in the surgical field.

[0096] Typically, the focusing range may be between 180 mm and 600 mm, for example. This focal length refers to the distance between the outer surface of the last lens of an imaging or viewing system associated with the device, and the point where the laser beam is focused. Schematically, in Figs. 1 and 11 the last lens of the optical system associated with the device 1 is indicated by the reference number 11. The device 1 may comprise a locking mechanism for locking the viewing system, for example a dovetail mechanism, indicated by the reference number 2 in Figs. 1 and 2. This mechanism makes it possible to secure the viewing system with the outer surface of the lens 11 at a distance from the mirror 9 equal to the distance between this mirror and the exit opening 5 of the device 1. In some cases, a set of adapters may be used to interface the device 1 with different viewing systems. The length of 180-600 mm referred to the focusing range is the distance between the focal point of the beam and the face of the lens 11 facing the mirror 9, i.e., in other words, the distance between the exit opening 5 and the focusing point, namely the focus F27 of the concave mirror 27.

[0097] In surgical applications, the working area, i.e. the area along which the focus F27 can be moved by oscillation around the X- and Y-axes, may be a circular area having a diameter up to 70.5 mm at a focal distance of 400 mm.

[0098] The opening of the scanning cone (see Fig. 8) may preferably be within 10°, more preferably (as mentioned above) within 8°.

[0099] The fast scanning mechanism, which comprises the scanning mirrors 15, 19 and the respective actuators 17, 21, may have a pass band, for example, of up to 5000 Hz, preferably greater than 2000 Hz, and a settling time between 50 and1000 microseconds, preferably less than 200 microseconds.

[0100] By definition, the pass band of the scanning mechanism is the maximum frequency of the input signal for which a response of the output signal is reduced by 0.71x (-3dB). For example, with a pass band of 1 kHz, if a 100 Hz signal (a frequency much lower than the pass band) is applied in order to cause the laser beam to cover a 1 mm line, the system responds with a line having a width of 1 mm. If the frequency is increased while maintaining the same amplitude of the signal, the size of the line decreases. When the frequency of 1 kHz (equal to the pass band) is reached, the line will have a width of 0.71 mm. If the frequency is further increased, the width of the line would "collapse." Therefore, the pass band does not represent the upper limit of the maximum frequency at which the system can operate, but exceeding this limit is not useful, because the output signal obtained would be too small.

[0101] The settling time refers to the scanning and corresponds to the minimum time required by the system to move a point (laser spot) from one stationary position to another stationary position, irrespective of whether the laser is switched on or off.

[0102] The settling time of the fast scanning mechanism is particularly interesting in the case of use of continuous discharge laser sources, or in any case of laser sources which cannot be modulated at high speed. In this case, since it is not possible to switch the laser beam on and off in short times, it is important to have fast scanning, which acts as a modulator of the laser action on the tissues. A typical example is a dotted line made with a laser beam that is always on. In this case, it is the fast scanner, i.e. the scanning mechanism 13, that makes the laser spot stay on the individual points and translates the spot from one point to another at high speed.

[0103] The focusing device described above, which uses the optical sources 81, 83 and a special focusing optics comprising the concave oscillating mirror 27, is only one possible embodiment. Figs. 14 through 23 show further embodiments of the dynamic focusing device, based on the use of two auxiliary or secondary optical beams, and of a fast scanning mechanism, or scanner, similar to the fast scanning mechanism 13 described above.

[0104] Specifically, with initial reference to Figs. 14 through 22, this embodiment illustrates a focusing device for focusing an optical beam, especially a power opticalbeam to be focused, in its essential components, which can be contained in a housing.

[0105] The reference number 100 indicates the whole focusing device. A housing containing the focusing device is schematically indicated with the reference number 103. The housing comprises an entrance opening 103.1 and an exit opening 103.2, for the entrance and exit of a beam to be focused, hereinafter referred to as "power laser beam", for the sake of clarity.

[0106] The letter T indicates a target surface onto which the power laser beam is to be focused. FL indicates the power laser beam exiting the focusing device 100, focused on the surface T. For simplicity, the power laser beam FL is indicated by a straight line, which represents its axis of propagation.

[0107] The focusing device 100 comprises a focusing optics 105, arranged inside the housing 103. Analogously to the previously described embodiment, the focusing optics 105 operates as a beam expander. It comprises a focusing lens 123, preferably stationary within the housing 103, having a function analogous to the focusing lens 23, and a movable optical element 127, having a function analogous to the concave mirror 27 with regard to the focusing of the power laser beam FL.

[0108] In the embodiment illustrated in Figs. 14 through 22, the movable optical element 127 is schematically represented as a lens. It may consist of a single lens or a lens assembly, and thus be an element having optical power in transmission. In other embodiments, as in the figures previously described, the movable optical element 127 may be or comprise a concave mirror, that is, an element having optical power in reflection.

[0109] To focus the power laser beam FL onto the target surface T, that may be at a variable distance from the focusing device 100, the movable optical element 127 is provided with a movement according to fl27 in a direction parallel to an optical axis A105, of the focusing optics 105. In Fig.14, the optical axis A105 coincides with the line representing the axis of the power laser beam FL.

[0110] The movement of the movable optical element 127 according to fl 27 toward, and away from, the fixed focusing lens 123 can be achieved by means of any suitable mechanism, servo-assisted or manual, for example by mounting the movable opticalelement 127 on a movable slider by means of a ring as described above.[oni] The focusing device 100 comprises a fast scanning mechanism 113, analogous to the fast scanning mechanism 13 described above.

[0112] In some embodiments, the focusing device 100 comprises a first scanning mirror 115 along an optical path between the entrance opening 103.1 and the focusing optics 105. The first scanning mirror 115 is controlled by an actuator 117 that controls a scanning movement of the first scanning mirror 115 around a first scanning axis XI. The fast scanning mechanism 113 also comprises a second scanning mirror 119, arranged along the optical path followed by the power laser beam, between the entrance opening 103.1 and the first scanning mirror 115. In practice, along the optical path followed by the power laser beam FL to be focused, the power laser beam FL encounters first the second scanning mirror 119, and subsequently the first scanning mirror 115. The second scanning mirror 119 is controlled by an actuator 121 that controls a scanning movement of the second scanning mirror 119 around a second scanning axis Yl, that is not parallel to the first scanning axis XI, for example oriented at 90° with respect thereto.

[0113] Since the second scanning mirror 119 is the first mirror encountered by the power laser beam FL along its path, the second scanning mirror 119 is positioned so as to reflect the power laser beam FL - that is, the optical beam to be focused - which enters the housing 103 through the entrance opening 103.1, toward the first scanning mirror 115.

[0114] Moreover, the focusing device 100 comprises an optical assembly 130 for generating secondary beams, configured to emit a first secondary optical beam and a second secondary optical beam, both at a visible wavelength and mutually offset. In the embodiment of Figs. 14 through 22, the optical assembly 130 for generating secondary beams comprises a first auxiliary optical source 181 and a second auxiliary optical source 183 (hereinafter also referred to briefly as "optical sources"), which may consist of two laser sources, for example two micro-lasers, such as the auxiliary optical sources 81 and 83 described above with reference to the previous embodiment.

[0115] FS1 and FS2 respectively indicate the first secondary optical beam and the second secondary optical beam that are emitted by the optical sources 181 and 183,respectively. When the auxiliary optical sources 181, 183 are laser sources, the two secondary optical beams FS1, FS2 are laser beams. Therefore, they can be referred to as "secondary laser beams."

[0116] The focusing device 100 briefly described above can operate in three distinct conditions, illustrated respectively in Figs. 14, 15, and 16, Figs. 17, 18, and 19, and Figs. 20, 21, and 22.

[0117] The three conditions are achievable, as will become clear below, by acting on the position of the scanning mirrors 115, 119 and / or by selectively activating and deactivating the optical sources that generate the beams FS1, FS2 and FL. Deactivation may be achieved by switching off the respective source, or by inserting a shutter along the path of the respective optical beam.

[0118] In the first condition, illustrated in Figs. 14-16, the device is in a working configuration, i.e. with the power laser beam FL (originating from an external power laser source 20) directed onto the target surface T, on which it has previously been focused. Furthermore, the first secondary optical beam Fl and the second secondary optical beam FS2 do not pass through the focusing optics.

[0119] The optical beam to be focused, i.e. the power laser beam FL, impinges on the second scanning mirror 119 and is directed by the scanning mechanism, via sequential reflection on the second scanning mirror 119 and on the first scanning mirror 115, into an acceptance angle of the focusing optics 105, so as to exit from the focusing optics 105 and be focused onto the target surface T.

[0120] In some embodiments, in order to ensure that in this first condition the first secondary laser beam FS1 and the second secondary laser beam FS2 do not pass through the focusing optics 105, the two auxiliary optical sources 181, 183 may be switched off.

[0121] In other embodiments, in order to ensure that in this condition the secondary laser beams FS1, FS2 do not pass through the focusing optics 105, the optical sources 181, 183 and the scanning mirrors 115, 119 may be arranged in such a way that both secondary laser beams FS1 and FS2 are directed outside the acceptance angle of the focusing optics 105.

[0122] In still further embodiments, one of the two optical sources 181, 183 may be switched off and the other may be positioned, in combination with the scanning mirrors 115, 119, so that the respective secondary laser beam is directed outside the acceptance angle of the focusing optics 105.

[0123] An aiming laser source 202, generating a visible-wavelength aiming laser beam, may be associated with the power laser source 200. The two laser sources 200, 202 are configured, by means of special relay optics, so that the power laser beam FL and the aiming laser beam coincide spatially, to enable the operator to physically see the point of incidence of the power laser beam FL on the target surface T, when the power laser beam FL is at a non-visible wavelength.

[0124] The two secondary laser beams FS1, FS2 do not reach the target surface T and therefore do not interfere with the use of the power laser beam FL.

[0125] In order to perform the focusing of the power laser beam, the focusing device 100 is alternately brought into a second condition (represented in Figs. 17-19) and into third condition (represented in Figs. 20-22), switching at a high frequency between them.

[0126] In the second condition, the first secondary optical beam FS1 and the power laser beam FL to be focused do not pass through the focusing optics 105, while the second secondary optical beam FS2 impinges on the second scanning mirror 115 and is directed by the scanning mechanism 113 within the acceptance angle of the focusing optics 105, in a direction parallel to the optical axis Al 05 of the focusing optics 105, but spaced from it.

[0127] In this configuration, the power laser beam FL, i.e. the optical beam to be focused, can be switched off. Alternatively, the geometric arrangement of the scanning mirrors of the scanning mechanism 113 and the focusing optics 105 may be configured so that the path of the power laser beam does not enter the acceptance angle of the focusing optics. In both cases, the condition that the power laser beam FL does not pass through the focusing optics 105 is satisfied. For safety reasons, regardless of the geometric configuration, it is advisable that in this phase the power laser beam be switched off, where "switched off may also mean that the source 200 is on, but the power laser beam is intercepted along its path upstream of the focusing optics 105, soas not to reach it.

[0128] For the first secondary laser beam, i.e. for the first secondary optical beam FS1, various ways may be used to prevent it from entering the focusing optics, namely: switching off the auxiliary optical source 181; intercepting the secondary optical beam FS1 along its path upstream of the focusing optics 105; or arranging the auxiliary optical source 181 and the scanning mechanism 113 geometrically in such a way that the path of the secondary optical beam FS1 does not enter the acceptance angle of the focusing optics 105.

[0129] As shown in Figs. 17, 18, and 19, in this condition, the secondary optical beam FS2 reaches the target surface T along a path inclined with respect to the optical axis of the focusing optics 105, specifically converging toward it in the direction of propagation of the secondary optical beam FS2.

[0130] The third condition that the focusing device may take is illustrated in Figs. 20, 21, and 22. In this third condition, the second secondary optical beam FS2 and the optical beam FL to be focused do not pass through the focusing optics 105, while the first secondary optical beam FS1 impinges on the second scanning mirror 115 and is directed by the scanning mechanism 113, via the first scanning mirror 115, within the acceptance angle of the focusing optics 105, in a direction parallel to the optical axis of the focusing optics, and spaced from it.

[0131] This condition can be achieved similarly to the second condition, by suitably switching off and / or directing the power laser beam FL and the first secondary laser beam FS1 outside the acceptance angle of the focusing optics 105.

[0132] Since the secondary laser beams or secondary optical beams FS1, FS2 in the second condition and in the third condition enter the focusing optics 105 along a propagation direction parallel to the optical axis of the focusing optics, but spaced from it and offset from each other, the secondary laser beams generate, on the target surface T, a single spot, or two mutually superimposed spots centered on the optical axis Al 05, only if the focus of the focusing optics 105 lies on the target surface T.

[0133] During a focusing phase, the focusing device 100 may be controlled so that it repeatedly and at a high frequency switches from the second condition to the thirdcondition and vice versa, at a speed greater than a persistence time - on the retina of the eye of an observer who is viewing a target surface T - of an image of the spot of the first secondary optical beam FS1 and of the spot of the second secondary optical beam FS2.

[0134] In this way, the observer viewing the target surface T sees two distinct spots spaced from the point of intersection between the optical axis Al 05 and the target surface T, the two spots being formed by the secondary optical beams FS1, FS2 and are separated from each other. Only when the device is focused on the target surface T, the two spots are superimposed on each other or become concentric. Focusing is performed by adjusting the distance between the focusing lens 123 and the moving optical element 127.

[0135] For easier focusing, it may be provided that, in the second operating condition and in the third operating condition, one or both of the scanning mirrors 115 and 119 perform small cyclic oscillatory movements around their respective axes, while maintaining the orientation condition of the respective secondary optical beam FS1, FS2 within the acceptance angle of the focusing optics 105. In this way, the spot formed by each secondary optical beam FS1, FS2 is not a simple point, but instead an image will be formed, for example a straight line segment (with oscillation of only one scanning mirror) or a closed line figure, for example an ellipse or a circumference (with combined oscillation of both scanning mirrors 115, 119). In this case, focusing is achieved when the two straight line segments are superimposed on each other, or when the two closed figures are concentric with respect to each other (if of different size) or superimposed on each other (if of equal size).

[0136] In the various embodiments described herein, the optical sources, in particular the laser sources, and the scanning mechanism can be interfaced with a control unit 301 (see Figs. 14, 17 and 20). A similar control unit may be provided in the other embodiments described above, and has been omitted from the related figures for simplicity.

[0137] Through a human-machine interface, the operator can command the focusing device to assume the first condition (activation and use of the power laser beam), or the second and third conditions (focusing phase).

[0138] Other embodiments can be achieved by variation of those illustrated so far.

[0139] For example, in some embodiments one of the two auxiliary optical sources 181, 183 may be replaced by the aiming source 201. In this case, depending on which of the two auxiliary optical sources 181, 183 is replaced by the aiming source 201, in the first condition assumed by the focusing device the secondary optical beam of the remaining auxiliary optical source does not pass through the focusing optics 105, while the aiming optical beam passes trough the focusing optics together with the power laser beam FL. The second and third conditions described above are implemented in the same way, with the only difference that one of the two auxiliary optical sources is represented by the aiming source 202, while the other auxiliary optical source will be constituted by the optical source 181 or by the optical source 183.

[0140] In other embodiments, instead of providing two auxiliary optical sources 81, 83, or 181, 183, it is possible to provide a single auxiliary source and a beam splitter that, from a single beam emitted by the auxiliary source, generates two secondary optical beams FS1, FS2. In this case, keeping the single source switched on, the alternate switching off of one or the other secondary optical beam is obtained by a suitable shutter (single or double) arranged along the optical paths of the two secondary optical beams.

[0141] An embodiment of this type is schematically shown in Fig. 23, which corresponds to Fig. 15 described above, where equal numbers indicate equal parts already shown in Figs. 14 through 22 and not described again. In Fig. 23, a single auxiliary optical source 182 is shown, which emits a single secondary beam FS that is split in a beam splitter 205 to form a first secondary optical beam FS1 and a second secondary optical beam FS2. The two secondary optical beams FS1, FS2 impinge on the second mirror 119 in the same way as shown for the secondary optical beams FS1, FS2 of Figs. 14 through 22. Along the two paths of the secondary optical beams FS1, FS2, respective shutters 207.1, 207.2 are provided, which intercept the two beams FS1, FS2 to perform the functions described above.

[0142] In the above description of embodiments, specific reference has been made to surgical applications. However, the use of the dynamic triangulation focusing device described is not limited to surgical applications, but can be advantageously employedwith similar benefits in other applications where it is necessary to precisely focus an optical beam, particularly a laser beam. For example, the focusing device may be advantageously used in laser marking machines in the industrial field, or in other laser equipment for industrial use.

[0143] Exemplary embodiments have been described above and are illustrated in the attached drawings. Those skilled in the art will understand that various modifications, omissions, and additions may be made to what has been expressly described herein, without departing from the scope of the invention as defined in the following claims.

Claims

CLAIMS1. A device for focusing an optical beam, especially a laser beam; wherein the device comprises:(a) a housing with an entrance opening for the optical beam to be focused and an exit opening for the optical beam to be focused;(b) in the housing, a focusing optics having an optical axis;(c) in the housing, a scanning mechanism for scanning the optical beam to be focused, positioned between the entrance opening and the focusing optics; wherein the scanning mechanism comprises:- a first scanning mirror along an optical path between the entrance opening and the focusing optics; the first scanning mirror being controlled by an actuator that controls a scanning movement of the first scanning mirror around a first scanning axis; and- a second scanning mirror along the optical path between the entrance opening and the first scanning mirror; the second scanning mirror being controlled by an actuator that controls a scanning movement of the second scanning mirror around a second scanning axis not parallel to the first scanning axis; the second scanning mirror being positioned so as to reflect the optical beam to be focused, which enters the housing through the entrance opening, toward the first scanning mirror;(d) an optical assembly for generating secondary beams, configured to emit a first secondary optical beam and a second secondary optical beam, at a visible wavelength and offset in relation to each other; wherein the scanning mechanism, the focusing optics, and the optical assembly for generating secondary beams are configured so as to selectively take: a first condition, where: the optical beam to be focused hits the second scanning mirror and is directed by the scanning mechanism within an acceptance angle of the focusing optics; a second condition, where: the first secondary optical beam and the optical beamto be focused do not pass through the focusing optics; and the second secondary optical beam hits the second scanning mirror and is directed by the scanning mechanism within the acceptance angle of the focusing lens, in a direction parallel to, but spaced from, the optical axis of the focusing optics; a third condition, where: the second secondary optical beam and the optical beam to be focused do not pass through the focusing optics; and the first secondary optical beam impinges on the second scanning mirror and is directed by the scanning mechanism within the acceptance angle of the focusing lens, in a direction parallel to, and spaced from, the optical axis of the focusing optics.

2. The device of claim 1, wherein, during a focusing phase, the scanning mechanism, the focusing optics, and the optical assembly for generating secondary beams are controlled so as to switch from the second operating condition to the third operating condition and vice versa at a speed higher than the persistence time - on the retina of the eye of an observer viewing a target surface on which the optical beam to be focused is to be focused - of an image of a spot of the first secondary optical beam and of the second secondary optical beam on the target surface.

3. The device of claim 2, wherein the scanning mechanism is controlled in such a way that, in the second condition and in the third condition, at least one of the first scanning mirror and the second scanning mirror performs a scanning movement to move the optical beam that is directed within the acceptance angle of the focusing optics, and to generate a luminous figure visible on the surface on which the optical beam to be focused must be focused.

4. The device of claim 1 or 2 or 3, wherein the optical assembly for generating secondary beams comprises a first auxiliary optical source and a second auxiliary optical source housed in the housing and configured to emit respectively the first secondary optical beam and the second secondary optical beam.

5. The device of claim 1 or 2 or 3, wherein the optical assembly for generating secondary beams comprises a single auxiliary optical source and a beam splitter configured to generate the first secondary optical beam and the second secondary optical beam.

6. The device of any one of the preceding claims, wherein in the first condition: the first secondary optical beam and the second secondary optical beam are directed by the scanning mechanism outside the acceptance angle of the focusing lens; or both the first secondary optical beam and the second secondary optical beam are switched off; or the first secondary optical beam is switched off and the second secondary optical beam is directed by the scanning mechanism outside the acceptance angle of the focusing optics.

7. The device of claim 1 or 2 or 3, wherein the optical assembly for generating secondary beams comprises: an aiming source configured to emit an optical beam coincident with the beam to be focused, the optical beam generated by the aiming source constituting the first secondary optical beam; and an auxiliary optical source housed in the housing, adapted to generate the second secondary optical beam.

8. The device of claim 7, wherein in the first condition: the first secondary optical beam generated by the aiming source is directed, together with the beam to be focused, within the acceptance angle of the focusing optics; and the second secondary optical beam is switched off, or is directed by the scanning mechanism outside the acceptance angle of the focusing optics.

9. The device of any one of the preceding claims, wherein: in the second condition, the path of the first secondary optical beam is directed by the scanning mechanism outside the acceptance angle of the focusing optics, or the first secondary optical beam is switched off; and the optical beam to be focused is directed by the scanning mechanism outside the acceptance angle of the focusing optics, or is switched off; andin the third condition, the path of the second secondary optical beam is directed by the scanning mechanism outside the accent angle of the focusing optics, or the second secondary optical beam is switched off; and the optical beam to be focused is directed by the scanning mechanism outside the acceptance angle of the focusing optics, or is switched off.

10. The device of any one of the preceding claims, wherein the first secondary optical beam and the second secondary optical beam are laser beams.

11. The device of any one of the preceding claims, wherein the optical assembly for generating secondary beams is arranged so that the first secondary optical beam and the second secondary optical beam have optical axes which converge at a point located behind the second scanning mirror, with respect to the direction of propagation of the first secondary optical beam and the second secondary optical beam.

12. The device of any one of the preceding claims, wherein the focusing optics comprises a fixed focusing lens and a movable optical element; wherein the movable optical element comprises a lens movable relative to the focusing lens.

13. The device of any one of claims 1 to 11 , wherein the focusing optics comprises a fixed focusing lens and a movable optical element; wherein the movable optical element comprises a concave mirror provided with: a translatory focusing movement along a focusing axis, and a scanning movement around a neutral position; the concave mirror comprising an optical axis parallel to the axis of the fixed focusing lens when the concave mirror is in the neutral position; or with a translatory focusing movement along a focusing axis, but without a scanning movement; the concave mirror being coaxial with the fixed focusing lens.

14. The device of any one of the preceding claims, wherein the scanning mechanism comprises: a) a pass band between 0 Hz to 5000 Hz, preferably between 0 Hz and2000 Hz; or b) a settling time between 50 microseconds and 1000 microseconds, preferably less than 200 microseconds; or c) both a band between 0 Hz and 5000 Hz, preferably between 0 Hz and 2000 Hz, and a settling time between 50 microseconds and1000 microseconds, preferably less than 200 microseconds.

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